>It works better if you use AC, since then you don't get (permanent)
>electrolysis of the solution. If you want a safe demonstration, use a few
>volts AC from a double-wound transformer.
Since I only needed it to work for a few minutes to show the concept, I
knew I could get away with the MUCH safer DC current (at least much safer
in the eyes of the collage and their liability insurance. It's easy to
convince someone they won't be electrocuted by playing with water and a 9
volt battery... not as easy to convince them of that with anything that
plugs into a wall).
And to get it to work again really only involved pulling the metal plates
out of the jar, rubbing them clean, and then replacing the water with a
fresh batch of tap water and salt. So it did well for its purpose, and
the teacher was happy that he could keep it and "reset" it to show other
classes.
>Although, as I am sure you know, these 'water dimmers' were used (in my
>lifetime, just) for full-sized theatre lights, running directly off the
>mains. Topping them up when live was dangerous. As was finding the darn
>things nearly boiling during a play.
Yup... we were studying different dimmer technologies that have been
around.
The one I wanted to make, but couldn't get to work right (probably not
enough power, and I wasn't about to start messing with the levels
needed), was "carbon nail" dimmers, for lack of the correct term that I
can't think of right now (and all my theater books are in my parent's
basement, so I can't look them up).
These were pretty much the direct design predecessor to slightly more
modern resistance dimmers. The concept was a whole bunch of nails were
driven into a wheel, and they all hit a center wheel where the power wire
was attached. Based on which nail the circuit was completed thru, the
power had to go thru more and more of the only slightly conductive metal,
so the lights got brighter and dimmer as you rolled the wheel and changed
which nail was the contact point.
Apparently, they were rather dangerous, as the nails all had some carbon
powder on them, and it would flake off and release as a dust as they were
used. The nails also had a tendency to go bad while in use, and you had
to pull out the old one, and hammer in a new one. That could cause much
shorting (usually thru the person wielding the hammer), and tended to
cause the fine carbon powder to flash.
Can't say I have any personal experience with them, so the above
"dangers" are purely what I remember reading in the books.
-chris
<http://www.mythtech.net>
Here's something I just got...maybe someone here can help him out.
Jeff
>Status: U
>Date: Mon, 10 Jun 2002 19:42:00 -0400
>From: "Eric Einem" <hopeful(a)einem.us>
>To: <jhellige(a)earthlink.net>
>Subject: Hercules InColor Card needed
>
>Dear Jeff Hellinge,
>
>Hercules InColor Card needed.
>
>I am in need of five Hercules InColor EGA Cards (P/N GB222). I am
>willing to pay $100 each for one or more.
>
>Do you have any of these adaptors you could sell?
>
>Thanks,
>
>Eric Einem
>CSTS, Inc
>hopeful(a)einem.us
>714-961-2787 ext. 208
--
Home of the TRS-80 Model 2000 FAQ File
http://www.cchaven.comhttp://www.geocities.com/siliconvalley/lakes/6757
>Wait a week? The professional electronics suppliers over
>here offer next-day service as a matter of routine. If
>you pay extra, they'll guarantee to deliver by 9am.
>
>Do U.S. suppliers not offer that?
I know I can get that with MCM Electronics, but usually next day is
really next next day (for some reason whenever I try to do next day, they
screw it up and it doesn't ship until the next day, making it 2 day
delivery).
My only problems with dealing with other sources than Rat Shack, is when
I need one or two cheap items. Sure, RS charges more for the item, but
when I am talking about $2 parts, the shipping alone will cost more than
the higher rate RS is charging. The other issue is some mail order
warehouses have minimum order prices. So again, when you only need $4
worth of parts, but they have a minimum of $25 orders, RS starts to look
better and better. (I can drive 5 minutes to the Mall, ignore the sales
drones, pay $6 for $4 worth of items, and get my project done today... or
I can mail order the parts, pay $25 for $35 worth of stuff where I only
NEED $4 of it right now, plus $7 on shipping, and wait a week, or $25 on
shipping and get it "next day", and finish my project in two days to a
week).
Needless to say, Rat Shack still gets a chunk of my business... although
I do try to pool projects so I can make the $25 minimum order, and then
just use ground shipping and wait a week. But there are times when that
just isn't reasonable to fit my deadlines.
-chris
<http://www.mythtech.net>
Hi,
I've been bitten by the collecting bug - I've got three "vintage"
computers and now I want more... Sooo... Anyone got any single-board
computers/microprocessor trainers they can bear to part with? I'm aiming for
the following SBCs in particular, but I'm interested in anything that's
either single board or fairly small (interconnected Eurocards? Think "Acorn"
then think "System 1").
And now for the wants list:
Synertek SYM-1 or SY-VIM-1
MOS KIM-1
Rockwell AIM65 (with or without printer, with or without case)
Compukit UK101
Anyone with any of these machines fancy parting with them?
Thanks.
--
Phil.
philpem(a)dsl.pipex.com
http://www.philpem.dsl.pipex.com/
_______________________________________________
cctech mailing list
cctech(a)classiccmp.org
http://www.classiccmp.org/mailman/listinfo/cctech
Sellam Ismail <foo(a)siconic.com> wrote:
> What is the "comb. keyboard"? Combination? At any rate, maybe I can move
> tube #8 into the #6 position and play around with it in that configuration
> and see what happens.
I'm thinking that 026 and 029 keypunches could be had with several
types of keyboards. "Numeric" would only have numeric keys, because
if numbers are all you want to punch then giving the operator the
ability to easily punch letters and figures opens up all sorts of
possibility for error. "Combination" would have a full keyboard that
could be used to punch letters and figures as well as numbers.
The 029 could be had with two different character sets as well, one
commercial and one scientific. The differences were only in the
keycap legends and what was printed on top of the card though; the
same key positions produced the same punches on both.
-Frank McConnell
So I'm off to look for a 25L6 tube for my IBM 026. John Lawson says that
the tube is a 25L6 because all the other tubes in the rack are 25L6 types
and he believes they are hammer drivers. Not to doubt the venerable
Mr. Lawson, since he did used to service these, but I just want to make
sure this is in fact the right tube type that goes into the socket that is
currently empty. See photo here:
http://www.vintage.org/gallery.php?title=IBM%20026%20Printing%20Card%20Card…
I'd hate to plug in the wrong tube and then witness volumnious
amounts of smoke billow from within the machine. Can someone verify that
the 25L6 is indeed the correct tube for the empty socket?
Thanks!
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
I've got 50-pin SCSI-2 connectors inside my MicroVAX 3100. Is there a
way to use 68-pin devices? The RZ26L and RZ28's in it are 50-pin, but I
have some RZ29's that are 68-pin and I'm wondering if there is in
adapter? I suspect not, but just asking.
If I'm not mistaken, it is possible to "go the other way" and use 50-pin
devices on a 68-pin cable with an adapter that terminates that "extra"
lines, correct?
- Bob
> -----Original Message-----
> From: Brian Chase [mailto:vaxzilla@jarai.org]
> When I power up the system, with monitor attached, the
> internal cooling
> fan spins up, the hard drive spins up (and sounds normal), and the
> machine chimes what I seem to recall as being the regular
> start up sound
> for this era of Mac. However, the display remains dark. If
> I power off
> the Mac, leaving the monitor on, the monitor makes a light
> static/crackle noise; it's the sort of sound I normally
> associate with a
> monitor that's lost the video input signal. I've played with the
> brightness and contrast controls without any success.
Would you believe that the whole thing may be working? ;)
First thing to do would be re-initialize the "parameter RAM." Hit
command-alt-p-r on power up. (I have seen corrupted PR cause this
kind of problem.) There are also a couple of things that you can
(very safely) reset with other hot-keys. You'll have to look them
up, though.
You might check to see if there's any flash or what not on the monitor
when the computer comes on. If the monitor has a power-save mode, and
starts up that way, does it turn on at all?
... but now that I read the next paragraph :)
> If I switch the other monitor, the behavior is the same. If I switch
> from the orginal motherboard to the one I purchased on eBay, the
> behavior is the same. It's possible both monitors are bad and/or both
Very strange. What's common between the two boards? Do you have, or
can you get, a known-good monitor?
Are you using the same RAM in both boards? That could be suspect. If
you've been plugging the drives back into the board, don't. Take
everything out -- including un-used cables -- except what's absolutely
necessary. Try again that way.
> motherboards are bad. I don't have a multimeter to verify that the
> voltages coming out of the PS are correct. Nor do I know
This is also a problem. Just a stab in the dark, try blowing the board
out. I've seen some strange dust-bunny related problems with macs. :)
Make sure there's no way the board can short itself out to ground
somewhere...
... and get a multimeter.
> that the hard
> drive is functional--but I'd assume that nothing needs to be
> loaded from
> the HD in order to get the display to come up.
Nope, but again, take it out, and the floppy, and whatever else (boards,
etc) you can. Bad hardware makes computers do funny things.
> I'm a bit puzzled, and wondering if anyone here with insight on these
> Macs and their displays can give me any additional pointers.
Err -- you could also get an adaptor to plug a vga monitor in, and use
a monitor you know works, to eliminate that possibility.
Chris
Christopher Smith, Perl Developer
Amdocs - Champaign, IL
/usr/bin/perl -e '
print((~"\x95\xc4\xe3"^"Just Another Perl Hacker.")."\x08!\n");
'
>I have one (got the ethernet off of a IIsi that was $5 at the
>Uni Surplus depot) I haven't considered NetBSD, though. I _do_
>have a couple of sets of 30-pin 16MB SIMMs - 128MB in an SE/30
>would be fine. :-)
Might not be possible.
The SE/30 has 8 30 pin slots, and is rated to use a max of 4 MB chips.
That gives it a max RAM of 32 MB.
But I haven't tried putting more in one, and there are a few Macs out
there that will use larger chips, or more RAM than they are rated for,
but most will not (they either don't see the larger chips, or they won't
access more RAM).
-chris
<http://www.mythtech.net>
